CASE STUDY: IMPACT OF HYPODERMA LINEATUM UPON LIVE GROWTH, CARCASS ATTRIBUTES, AND HIDE VALUE OF FED BEEF CATTLE By: Daniel E. Guadián García A THESIS submitted in partial fulfillment of the requirements for the degree MASTER OF SCIENCE Major Subject: Agriculture Emphasis: Animal Science Department of Agricultural Sciences West Texas A&M University Canyon, TX December 2016 ABSTRACT A case study was done at the West Texas A&M University Research Feedlot, Canyon, from 14 November 2014 to 5 August 2015. While processing crossbred bulls (n=32) upon arrival (d0), some animals in the load of cattle were identified to be infested with grubs, later identified as the common cattle grub, Hypoderma lineatum (Villers). Metaphylaxis was administered upon arrival (d 0) to the feedlot; additionally, cattle were vaccinated against respiratory viruses, dewormed, and individually identified. Cattle were placed on a starter ration (d0) and transitioned to a finishing ration by d45. Twelve days after arrival, all cattle were re-weighed and manually palpated to quantify infestation by grubs; a hide map was used to record the location of the individual grubs. Grubs were manually extracted from the left side of infested animals to assess potential need for physical removal; right side grubs remained in the animals. Also, on d12, animals were administered a growth-promoting implant, and band-castrated. Two grub- infested cattle were slaughtered (d18) at the WTAMU Meat Laboratory to document hide damage; hides were manually fleshed and converted into rawhide. Two animals (grub- free) died from bovine respiratory disease during the study period (d15, d50). The remaining cattle were reweighed (d12, d40, d70, d96, d124, d152, d180, d208, d234, d236, and d264) to assess potential differences in growth rate. Cattle were slaughtered in two groups (n=9 on d234; n=19 on d264) at a local beef processor. Data collected during slaughter and grading processes included individual animal identification, liver score, hot i carcass weight, longissimus muscle area, 12th rib subcutaneous fat depth, kidney- pelvic-heart fat, yield grade, marbling score, and quality grade. Hides were individually identified and tracked through the facility to hide processing. Hides were green de- fleshed, lime de-fleshed, and de-haired for 24 h. Hides were then exposed to blue- chroming chemicals for 24 h; subsequently, blue-chrome hides were individually graded as #1, #2, or #3 hides. No difference in initial weight (P = 0.89), finished weight (P = 0.35), average daily gain (P = 0.59), hot carcass weight (P = 0.38), longissimus muscle area (P = 0.91), 12th rib subcutaneous fat depth (P = 0.64), calculated yield grade (P = 0.84), or kidney-pelvic-heart fat (P = 0.38) was detected between grub-free and grub- infested cattle. Grub-infested cattle tended to have more marbling (P = 0.07) than grub- free cattle. No difference in hide damage or value occurred between left sides (manually extracted) and right sides (grubs allowed to remain). Infestation by grubs did not negatively affect growth or carcass attributes. Hide damage in feeder calves resolved during the finishing period and grub-damaged hides met #1 criteria. Timely application of avermectin can prevent this problem from reducing beef system value. ii ACKNOWLEDGMENTS This thesis is dedicated to my parents who have given me the opportunity of an education from the best institutions and support throughout my life. This master’s thesis would not have been possible without the guidance and the help of several individuals who in one way or another contributed to my education and contributed their valuable time and effort in the development and completion of this study. I wish to thank the members who served on my thesis committee, Dr. Ty Lawrence, Dr. Bonnie Pendleton, and Dr. John Richeson. I am heartily thankful to my supervisor, Dr. Ty Lawrence, whose encouragement, guidance and support from the initial to the final levels enabled me to develop an understanding of agriculture. I am very thankful to him for believing in me and giving me an opportunity to complete a master’s program under his supervision. Last but not the least; I want to thank my family and the One above all of us, for giving me the strength to continue fighting every day to better myself as an animal scientist as well as a person. I am indebted to everyone who has been a part of the one and only, Beef Carcass Research Center for continuous support throughout my educational career as well as this project. iii APPROVAL ___________________________________________________ Chairman, Thesis Committee Date ___________________________________________________ Member, Thesis Committee Date ___________________________________________________ Member, Thesis Committee Date ______________________________________________________ Head, Department of Agriculture and Natural Sciences Date ______________________________________________________ Dean, Department of Agriculture and Natural Sciences Date ______________________________________________________ Dean, Graduate School Date iv TABLE OF CONTENTS TABLE OF CONTENTS ................................................................................................................. v LIST OF FIGURES ....................................................................................................................... vii LIST OF TABLES .......................................................................................................................... ix CHAPTER 1 .................................................................................................................................... 1 INTRODUCTION ....................................................................................................................... 1 CHAPTER 2 .................................................................................................................................... 3 REVIEW OF LITERATURE ...................................................................................................... 3 2.1 History of the cattle grub ............................................................................................. 3 2.2 Development and life cycle of heel flies ...................................................................... 4 2.3 Seasonal occurrence ................................................................................................... 12 2.4 Historical impact of cattle grubs ................................................................................ 16 2.5 Losses due to cattle grubs .......................................................................................... 17 2.6 Factors of nature affecting grubs ............................................................................... 18 2.7 Housing and protection against heel flies .................................................................. 19 2.8 Methods to control cattle grubs .................................................................................. 19 2.8.1 Controlling grub infestation by manual removal ....................................................... 19 2.8.2 Dipping vats ............................................................................................................... 20 2.8.3 Rotenone .................................................................................................................... 21 2.8.4 Organophosphates ...................................................................................................... 23 2.8.4.1 Ruelene ..................................................................................................................... 24 2.8.4.2 Warbex ...................................................................................................................... 25 2.8.5 Avermectins .............................................................................................................. 26 2.8.6 Milbemycins ............................................................................................................. 29 2.9 Immune response and vaccination ............................................................................ 29 2.10 Bibliography ............................................................................................................ 31 3.1 INTRODUCTION ........................................................................................................... 47 3.2 ABSTRACT ..................................................................................................................... 47 3.3 Materials and methods ..................................................................................................... 50 3.3.1 Initial discovery and cattle processing .......................................................................... 50 v 3.3.2 Manual removal, castration, and further processing ........................................................ 51 3.3.3 Harvest in meat laboratory ............................................................................................... 51 3.3.4 Live animal growth .......................................................................................................... 52 3.3.5 Commercial slaughter and animal processing.................................................................. 52 3.3.6 Statistical analysis ............................................................................................................ 53 3.4 Results and discussion ....................................................................................................